The pantograph is also called bow collector which is the electrical equipment installed on the electric locomotive roof for receiving electric energy from the catenary. The pantograph is one of the key parts of the electric locomotive and plays a key role in high-speed safe and stable operation of the vehicles. Smoothness between the pantograph and the catenary is highly required for high-speed train during the running process, and a little error often leads to fault. Specifically, the motor train unit will receive power from the catenary by the pantograph to drive the locomotive to go ahead during the running process. The locomotive will be deenergized and out of control, even lead to train derailment when the pantograph and the catenary are detached to each other.
The pantograph for current electric locomotive is divided into double-armed, single-armed, vertical and Ishizu types. Wherein the double-armed pantograph is called “diamond” pantograph, some new railway vehicles have been modified into the railway vehicles having single-armed pantographs at present due to high maintenance cost and risk for pulling electric train wire apart; and some railway vehicles (e.g., shinkansen 300 series vehicles) are reformed into the railway vehicles having single-armed pantographs from these having original double-armed pantographs. The advantage of “Z” (<) shaped pantograph most commonly used is that it has less noise than that from the double-armed pantograph, the electric train wire is not easy to be pulled apart in case of any fault, and such pantograph is a common pantograph at present. The vertical pantograph is also called T-shaped (alary) pantograph suitable for high-speed running due to low wind resistance and capable of reducing noise during train working process, and mainly used for high-speed railway vehicles. Due to high cost, the vertical pantograph has never been used (the vertical pantograph is changed into single-armed pantograph from vertical pantograph when shinkansen 500 series vehicles of Japan are reformed). The Ishizu pantograph was invented by Shizu Ryusuke, the sixth generation president of Okayama Electric Tramway Co., Ltd. on 1951 and also called “Okayama Electric Type” or “Okayama Tramway Type”. Other pantographs are of serial-type structures except the double-armed pantograph.
Pantograph-catenary accidents in electric railway power failure and shutdown accidents account for about 80% of all accidents, the calculation of economic loss caused by pantograph-catenary accidents is fairly significant every year. Accidents including pantograph scrapping catenary or catenary scrapping pantograph caused by use of pantograph are currently serious. It shows that one suspension is dropped and the contact stripe of the catenary is knocked out for the mild case, the catenary lead and the messenger wire are dropped for the severe case when the post is dumped and the locomotive pantograph is completely damaged, resulting in catenary power failure and train running interrupted, etc. All these accidents will bring many difficulties and hazards to emergency maintenance in case of some special regional environment conditions. In recent years, innovation is made from the pantograph to the catenary to different levels so as to improve the technical performance of the equipment and reduce pantograph-catenary accidents, but the above problems have not been radically solved due to inherent defects on the structure of the pantograph.
Current collection quality of the pantograph and the contact wire of the electric locomotive mainly depends on the interaction between the pantograph and the catenary. To ensure the smooth flow of the traction current, a certain contact pressure must exist between the pantograph and the contact wire. If the contact pressure between the pantograph and the catenary is too low, the percentage of contact loss will be increased; if the contact pressure is too high, high mechanical abrasion will be produced between the sliding plate and the contact wire. The actual contact pressure between the pantograph and the catenary is composed of four parts: static contact pressure, which is a vertical force applied on the sliding plate through the pantograph ascending device to ascend the sliding plate; an up-down alternating dynamic contact pressure related to the equivalent mass and generated from the pantograph which vibrates up and down during the operation after the contact wire ascends to different levels under the rising function of the pantograph due to elastic difference in the contact suspension; an aerodynamic force, which rapidly increases with the increase of the speed and is generated from the pantograph due to the function of air flow during the operation; and damping force generated from all joints of the pantograph during the pantograph ascending and descending processes. In addition, the electric locomotive may bring large lateral force to the pantograph in case of side wind during the operation.
For the conventional pantograph which has limitation on inherent structure, the collector heads mainly move in vertical direction, preloading and buffering devices for damping are set in vertical direction only, but no damping device is provided in advancing direction and lateral direction of the vehicles. Moreover, the existing pantographs are not provided with head separation devices. The scrapers on the collector heads cannot be separated in case of pantograph-catenary scrapping, so the pantograph-catenary scrapping accident may easily occur. Some potential problems exist due to poor structural stability of the existing pantographs and little consideration of protection measures in lateral force loading and pantograph-catenary scrapping process.